Sinister Serpent (TFK-SP001) [TFK-SP001] Super Rare BT9-031 this effect only happens once

this effect only happens once

Set: World Championship 2008 DS Game Card type: Normal Spell Rarity: Super Rare Activate only when your opponent declares an attack

that monster gains ATK equal to the ATK of the opponent's monster it is battling

Set: Unlimited Edition Type: Enchantment Rarity: Rare Cost: {R}{R} At the beginning of each player's upkeep

Set: Commander 2016 Type: Legendary Creature — Merfolk Wizard Rarity: Rare Cost: {G}{U} {4}: Scry 1

Sinister Serpent (TFK-SP001) [TFK-SP001] Super Rare BT9-031 this effect only happens onceSet: The Falsebound Kingdom Card type: Effect Monster Rarity: Super Rare Attack: 300 Defense: 250